Due to rapid progress in the semiconductor industry and in electronic technologies, technologies for manufacturing infrared measuring sensors have also progressed significantly. Infrared measuring sensors not only apply to the medical purpose of measuring body temperature but also apply to scientific, commercial and military purposes, such as laser detection, missile guidance, infrared spectrometry, remote control, burglarproofing equipment and thermal image detection. Conventionally, infrared measuring sensors include thermal type infrared measuring sensors and photon type infrared measuring sensors. Since the thermal type infrared measuring sensor is utilized more conveniently, it is widely used in various applications.
Generally speaking, the thermal type infrared sensors are further classified into thermocouple infrared sensors, pyroelectric infrared sensors, and microbolometers. The thermocouple infrared sensor, also named a thermopile infrared sensor, is constructed of a plurality of series-wound thermocouples. Hot junctions thereof are arranged on a suspended membrane and cold junctions are coupled to a substrate. Leads between the suspended membrane and the substrate include a series of thermocouples, and therefore the leads are normally wide and short.
The microbolometer utilizes a thermal measuring membrane with a high temperature coefficient of resistance (TCR) to act as the suspended infrared measuring membrane on the substrate of a reading circuit chip. At least two leads support the suspended measuring membrane on the substrate, and electrical signals measured by the suspended measuring membrane are transmitted to the substrate by the leads for reading and processing the electrical signals by electric circuits on the substrate. The pyroelectric infrared sensor utilizes a pyroelectric material to act as the suspended measuring membrane. The leads of the suspended measuring membranes of the microbolometer and the pyroelectric infrared sensor must be few in quantity, long, narrow and thin to reduce thermal conductance thereof and still be strong enough to maintain solid connections.
However, residual stress exists in the suspended membrane and in the leads thereof as a result of the manufacturing processes. The residual stress can press hard upon the structure and especially at some structural connections. The structural connections are often manufactured of different materials and by different processes, and therefore, their mechanical strength is relatively weak. If the residual stress is larger than the junction strength of the connections, the connections may break. The leads must extend from the suspended membrane down to a conductive layer surface of the reading circuits in the substrate. However, the conductive membrane of the lead is very thin and therefore the mechanical strength of the connections are very weak.